LARGE MOTOR INSTALLATION AND STARTUP
by
William H. Miller
General Manager
Enprotech Corporation
Schenectady, New York
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William H. Miller founded REM Technol­
ogies, Incorporated, in 1984. He serves as
President and Principal Engineer. REM Pro­
vides numerous engineering services to mo­
tor and generator users.
Mr. Miller graduated from Cornell Uni­
versity as a Mechanical Engineer. He joined
the Elliott Company, as a Development En­
gineer, and concentrated on the analysis of
bearings, seals, and rotor vibrations. This
work gained him his first patent award for
invention of a high pressure shaft seal.
In 1976, he joined Ingersoll Rand Company. While there, he was
a co-author on a paper and was awarded the American Society of
Lubrication Engineer's Walter D. Hodson Award. Mr. Miller later
joined Mechanical Technology, Incorporated in Latham, New York,
where his research and development in the area of compliant foil
bearings produced four new and patented designs to improve foil
bearing performance.
Mr Miller went to General Electric Company's Materials and
Processes Laboratory in Schenectady, New York as a Rotordynam­
icist and Bearing Analyst. He transferred to the Large Motor and
Generator Department as Manager of Advanced Quality Control
Engineering. He was responsible for the design, implementation,
and auditing of the department's Government, Nuclear, and Com­
mercial Quality Control Programs. He was later Manager of Me­
chanical Design, and then Subsection Manager of Mechanical
Design of Medium Motor Redesign Project. His work in mechanical
design has resulted in seven patents, and four pending.
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INSTALLATION OF ASSEMBLED MACHINES
Tasks
Lifting and handling
· Unpacking
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Set air gap
Install ventilating and accessory parts
Make final check of alignment
Dowel bearing pedestals
Grout base
Make electrical connections
Make initial start, inspection and adjustments
Check centering of rotor (running endplay)
Dowel stator frame
Couple to driven apparatus
Startup
Machine parts should be handled carefully by personnel expe­
rienced in lifting and moving heavy equipment. Lifting slings
should be in good condition and be padded where contact is made
with finished machine surfaces. A spreader bar should be used
where lifting cables might otherwise crush the top edge of a part or
packing case.
Before attempting to lift any machine, check the outline drawing
for the lifting points and their limitations. Unless otherwise
specified on the outline drawing, eyebolts, lugs, etc., are intended
to support only the_ part to which they are attached. These devices
are not suitable, in general, for lifting the total weight of the
assembled machine. Failure to observe these precautions may
result in damage to the equipment, injury to personnel, or both.
Parts should be level when lifted. In some cases, the lifting device
(eyebolt, lug, etc.) cannot be located directly above or online with
the center of gravity, and auxiliary slings will be required to level
the load.
Some machines may be handled as an assembled unit. If so, the
outline drawing will note the location capability of provisions to
lift the entire assembled unit. Assembled units should be handled
in one piece by attaching a sling (or slings) to the lifting lugs on the
base, as indicated on the outline drawing. The outline drawing will
also show the position of the lifting lugs. Assembled units should
not be handled by attaching slings to the shaft, to the bearing
pedestals, or to the stator frame.
A machine assembled on a base must always be supported with
blocks at each bearing pedestal and stator foot. The supports
should keep the base level and flat, and must elevate the base so
that the stator (or any stator part) does not support any portion of
the weight of the machine. Slings must never be wrapped around
the rotor core or journals. A spreader bar or blocks should be used
to prevent the slings from bearing against the windings. Blocks,
if used, must bear on the rotor hub or spider, not on the windings.
The installation tasks and startup considerations necessary to
commission large electric motors are discussed. The tasks are
discussed in the usual installation sequence, but some series of
tasks may need repetition if the adjustment of one part affects an
earlier adjustment. When connecting to other machinery, confirm
that the installed machinery is properly mounted before attempting
to align or grout the motor or generator. Particular attention must
be taken in the alignment of machines for direct drive.
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Check drive coupling alignment
LIFTING AND HANDLING
ABSTRACT
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Align bearing pedestals and set endplay
Align couplings
Set machine on foundation
Level base
Align base with respect to connected machinery
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PROCEEDINGS OF THE TWENTY-SECOND TURBOMACHINERY SYMPOSIUM
The preferred method of supporting a rotor, other than in its own
bearings, is to use stands. Blocks or heavy timber cribbing may be
used if stands are not available. Whatever the support, provisions
should be made to prevent the rotor from rolling off the support,
and wooden pads should be used on the steel stands to avoid marks
on the machined shaft surfaces. The bearing journals should not
be used as a location for the supports when the rotor is set down,
and they must be protected during handling.
An alternate method of setting down a rotor is to support the
rotor core with a padded cradle shaped to conform with the
curvature of the core. The length of the cradle must be longer than
the iron of the core, and when supporting a rotor, the cradle must
be centrally positioned under the iron core to avoid application of
pressure to the end connections of the armature winding. The
width must be at least one-fifth of the rotor diameter, but a greater
width may be desirable to prevent the rotor from rolling.
In no case shall the rotor be stored for any length of time by
supporting the rotor in a cradle, since permanent damage to the
core may result. This method should only be used during handling
of the rotor. Rotors should always be lowered slowly and carefully
into the cradle with axis of the shaft parallel to the rails of the cradle
to avoid damage from impact and point load.
Stators can be lifted as an assembly by the lifting lugs, if so
stated on the outline drawing. On larger machines, a spreader bar
should be used to obtain a vertical pull on each sling to avoid any
deformation of the frame.
Bases should be lifted by slings around the entire beam section.
The gussets between the top and bottom flanges are not designed
to serve as lifting lugs and should not be used for lifting. The
supports used during lifting should be so chosen as not to distort
the base.
UNPACKING
If the machine or machine parts have been exposed to a low
temperature, do not remove their coverings until they have had
sufficient time to attain a temperature that is nearly as high as that
of the room in which they are to be unpacked and located.
Otherwise, when opened, moisture will condense on the cold parts.
This may reduce the electrical resistance of insulations or cause
rust or corrosion of metallic parts. If the machine is shipped
disassembled, experienced personnel should check all journal and
bearing surfaces and repair any damage resulting from mishan­
dling or unprotected storage.
During shipment, the rotor of an assembled unit is restrained in
the axial direction by a temporary shipping device which clamps
the end of the shaft to the bearing pedestal. In the case of a single­
bearing machine, or section of a unit which is split for shipment
and without a bearing on one end, the shipping device is mounted
on the base and arranged to support the shaft and to provide a clamp
for constraint of axial movement. The shipping device must be
removed during installation when the machine is in place or (for
single-bearing units) when the shaft can be supported by the
mating shaft. When the shaft is clamped to a bearing pedestal, the
pedestal is doweled to the base with steel dowels. The machine or
machine parts should be inspected for dirt and foreign material
which may have accumulated during shipment and/or storage.
Particular attention should be paid to ventilation ducts, spaces
between poles, windings, and the spaces in the stator and spider
fabrications. Dry rags (no solvent) together with low pressure (35
psi maximum), high-volume dry air is recommended for this
cleaning. The direction of air flow must be carefully controlled to
avoid blowing foreign material into places even less accessible.
BASES AND FOUNDATIONS
All load-bearing portions of bases must be evenly supported
during the installation of a machine and, except for self-supporting
bases, the entire base acts only as a spacer between the machine
and the foundation. Bases ordered and designed to be self­
supporting should be so designated, and mounting requirements
should be shown on the outline drawing. Self-supporting bases are
shipped assembled and may be placed directly on a level foundation.
Bases of smaller machines are furnished as a single fabrication
which can be placed on the foundation without further assembly.
Larger machines and M-G set bases are built in sections to comply
with shipping or handling requirements and must be bolted togeth­
er after preliminary placement on the foundation. Joints between
mating sections should be aligned in the factory, adjacent sides
marked, and the joint doweled to simplify reassembly during
installation.
Usually, steel pads, each with two threaded holes, are located
inside the base, one at either side at each end of the base. These
pads are to facilitate attachment of the electrical grounding cables
to the machine in order to bring the machine exterior parts to a safe
ground potential. Before the grounding cables are bolted onto the
pads, the pad surfaces must have paint or rust removed by light
sanding or grinding so a good electrical contact can be achieved.
Consult the machine outline drawing for pad location, thread size,
and recommended grounding cable sizes.
Foundation caps are heavy cast iron or structural steel members
used in place of a base to distribute the weight of a stator foot or
bearing pedestal over a larger area of the foundation, thereby
reducing the stress in the foundation. Since the load-bearing parts
of the machine are independently supported by separate founda­
tion caps, lateral position as well as vertical position of the
machine parts must be maintained by the foundation. Like bases,
foundation caps must be evenly supported by the foundation
during installation, and continuously supported, i.e., grouted,
during machine operation.
The foot bolts holding the stator and bearing pedestals to the
base of machines shipped assembled are temporary, if the outline
drawing shows a foundation bolt extending up through the hole in
the base and the foot. The temporary bolt should be removed just
prior to lifting the assembled machine over the foundation to lower
it in place on the foundation bolts.
ALIGNMENT
The base should be initially positioned to provide as accurate an
alignment as possible with the connected machinery. The base
should be used to best divide the shaft endplay between both ends
of the controlling bearing to minimize movement of bearing
pedestals during final alignment. Base centerlines and bearing­
pedestal mounting-bolt patterns may be used as a guide. The
preliminary alignment of all bases for machines having three or
more bearings may be checked by installing the pedestals and
measuring to the bearing rocker seat using a laser optical system.
LEVELING
A high-grade, sensitive spirit level may be used to level small
bases which can be spanned by the level. Larger machines should
be leveled with a precision laser optical system. Sighting tech­
niques should be used which minimize instrument and systemic
errors.
A base warped or bent through improper handling may not rest
firmly on all supports with only the force of its own weight. It may
be necessary to assemble part or all of the machine on the base to
provide the additional weight needed to bring the base to the proper
level for alignment.
As an alternate procedure, the foundation bolts may be used to
pull the base to the leveling plates, grout pads, or other supports.
The base should first be aligned as accurately as possible, and the
bolts should be centered in the bolt holes. The foundation bolts
may then be anchored securely with grout. However, this grout
TUTORIAL ON LARGE MOTOR INSTALLATION AND STARTUP
should not restrict subsequent leveling and alignment of the base.
The foundation bolts should then be tightened and worked against
leveling screws or shims to level the base.
GROUTING
Before grouting the base, it is recommended that the machine
assembly and final alignment be completed and rechecked. Grout­
ing must be completed before operating the machine. If the grout
is prepared at the site, a cement/sand ratio of 1:2, with only enough
water to give a stiff mixture, is recommended.
If a commercially available grout mixture is used, the mixture
should be of high quality and mixed in accordance with supplier's
instructions. A rich, high-grade, nonshrink grout is recommended
for the space underneath the flanges and ribs of the base, and a
common cement grout is recommended for the space at the side of
the base within base box sections. To avoid any subsequent
expansion of the nonshrink grout, the exposed surfaces should be
sealed with either paint or at least one inch of common cement
grout.
The surface should be clean, rough, and thoroughly wetted, but
with free moisture removed. The grout should be rammed or
puddled under the base from only one side, and the surface of the
grout emerging from the opposite side should be removed and
discarded. Where the base is fabricated as a box section, the ribs
should be supported on a ridge of nonshrink grout and the balance
of the box section filled, through the access holes provided in the
top of the base, with common cement grout. Grout, especially
nonshrink grout which can be set within 20 minutes, should be
placed quickly to avoid working the grout after it starts to set.
Adding water to prolong the working time is not recommended.
Work the grout into all space up to and flush with the top surface
of the base, including spaces in foundation bolt holes which are not
filled by the eyebolt. Voids should be prevented. If the foundation
does not extend upward beyond the bottom of the base, provide
lateral support and cover the non-shrink grout under the base
flanges. To accommodate the thermal expansion of the steel base,
expansion material should be added to prevent foundation crack­
ing at the bottom of the curb. Voids should be prevented.
If a vibrator is used to move and settle the grout, it can cause
segregation of the components of the mixture and should be used
sparingly and with discretion.
CENTERING OF STATOR ON ROTOR
Airgap and end play adjustments should be made to ensure that
the stator is properly positioned with respect to the rotor. This is
usually done by shifting the stator until the location is correct.
After these adjustments, the stator should be secured to the base
with dowels. All pedestal and stator dowels should be in place
before the machine is operated under load.
RADIAL CENTERING (AIR GAP)
After the rotor, shaft, bearings and coupling have been aligned,
the stator should be positioned so that the rotor is centered in the
stator. Some frames have tapped holes in the footplates to permit
raising the frame with bolts bearing on the base. This facilitates
insertion or removal of shims from under the frame feet. Bolts
used to jack the frame should be removed after shimming and
should not be used as permanent support.
The radial "iron-to-iron" air gap is the distance from the circum­
ferential center of the pole face to the face of the rotor. It can be
best measured with a tapered gage and a fixed block gage, both on
extension handles long enough to reach the iron without interfer­
ence with the end turns. The tapered gage should be chalked, the
block gage positioned on the rotor iron, and the tapered gage
pushed firmly between the block and the stator iron. Read the
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tapered gage at the point of maximum penetration, as indicated by
the undisturbed chalk.
To obtain consistent results, the gage insertion force must be the
same for all measurements. A uniform air gap, measured from one
location on the armature surface by rotating the armature to four or
six points, spaced as equally as possible around each end of the
rotor circumference, is usually sufficient to ensure correct radial
centering of the rotor. The gap variance can be expected to be
within 0.02 in for a large machine. Repeat the procedure for the
opposite end.
AXIAL CENTERING (RUNNING ENDPLAY)
The total endplay of a rotor is established by the end-clearance
at the controlling bearing. However, the magnetic force tending to
axially center the rotor in the stator will, if the stator is not correctly
located with respect to the pedestals, cause the end of the journal
to ride or oscillate against the controlling bearing. With the stator
located correctly, the magnetic forces should hold the rotor within
the center one-third of the endplay, known as running endplay.
Before adjusting running endplay, it is essential that the shaft be
leveled and, with fields de-energized and the rotor turning, float
freely in the axial direction and assume no preferential position.
That is, the shaft should continue to operate at any axial position
without shifting of its own accord. The rotor of a motor operating
at weak field condition may be pushed in an axial direction by the
pressure of the ventilating air. The magnetic centering force may
be insufficient to counterbalance this force. The force thus being
exerted on the control bearing is small, and the bearing is normally
designed to handle this minor thrust intermittently.
While running with the specified volume of ventilating air
flowing through the machine, the axial operating position of the
shaft should be observed. If the operating position is not within the
center one-third of the endplay, the stator should be shifted axially
in the direction toward which the rotor must move to be centered
in the endplay. Check the radial air gap and readjust, if necessary,
then tighten the frame hold-down bolts and again check running
endplay. When satisfactory running endplay and radial air gap are
obtained, the frame should be secured to the base with dowels.
Machines which are connected through a flexible coupling to
equipment having an axially fixed shaft should have the running
endplay adjusted when the machine is uncoupled. When coupled
and running, the shaft position should be checked and corrections
should be made if a journal end is "drawn" to the bearing by the
coupling. Machines which are connected through a solid coupling
to equipment having an axially fixed shaft should have the rotor
core centered in the stator core by measurement from a reference
point on the shaft and stator, such as a shoulder or flange. When
determining the center of the core, do not include the end connec­
tions that extend beyond the iron of the core. While the mechanical
center may not correspond precisely to the magnetic center, the
thrust developed by any offset will be small and should not
significantly add to the axial force on the fixed shaft. If necessary,
the axial alignment may be refined after running the unit.
Windings should be checked, and any damage to the insulation
system, especially on end-turns, should be repaired.
The insulation should be tested and evaluated using a 500 volt
DC supply. The supply of the test potential should be current­
limited to avoid damage to insulation having a low insulation
resistance. The insulation resistance, while not a definite measure
of the dielectric strength of the insulation, is a useful indication of
the suitability of an insulation for operation or for further test at an
over-potential.
The resistance of any electrical insulation varies with the test
potential, the insulation temperature, moisture (in or on the insu­
lation), surface condition, and age. For a given test potential and
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PROCEEDINGS OF THE TWENTY-SECOND TURBOMACHINERY SYMPOSIUM
with known insulation temperature, the result of an insulation­
resistance test is thus dependent on the winding surface condition
and age as well as moisture content. The insulation-resistance data
must be properly interpreted to be of value. Each machine at each
installation will have an insulation-resistance history that is char­
acteristic of the particular machine and is helpful in deciding the
timing of corrective maintenance. It is recommended that insula­
tion resistance be measured and recorded each month.
For more information on the general theory, limitations and use
of insulation-resistance measurements, and the methods of obtain­
ing data, refer to the latest revision of the Institute of Electrical and
Electronics Engineers (IEEE) Standards, Publication No. 43, "Rec­
ommended Guide for Testing Insulation Resistance of Rotating
Machinery."
The duration of application of a test potential should be one
minute for an insulation-resistance measurement. Insulation­
resistance meters of the hand-cranked, generator type provide a
convenient, readily-portable method of obtaining an approximate
measurement; however, an electrically powered meter or measur­
ing circuit is recommended to provide the accuracy needed for
consistent periodic measurements made during the service life of
the machine. A correction factor should be applied to any insulation­
resistance value measured when the insulation temperature is
other than 40°C.
BEARING AND BEARING PEDESTAL INSULATION
The insulation resistance of each insulated bearing pedestal
should be periodically measured and the insulation corrected if the
resistance is less than 20,000 ohms, as indicated by a 500 volt
d-e insulation-resistance meter.
The shaft insulation of motors and engine-driven generators is
checked by measuring the insulation resistance of each insulated
bearing. The pedestal cap and upper bearing half is removed and
the shaft jacked to clear the lower bearing half. Measure the
insulation resistance of both upper and lower bearing halves. If the
lower bearing half shows low resistance, it may be necessary to
either slip a piece of clean, nonconducting paper between the
bearing and the journal, or roll the bearing out of the pedestal in
order to measure only the resistance of the bearing insulation.
After reassembling the bearing and pedestal cap, insert a thick­
ness gage between the shaft and the pedestal shaft seal and slide the
gage around the shaft. All metal parts should clear the shaft by
0.0 10 in to O.Q15 in.
ELECTRICAL CONNECTIONS
Before connections to the power and control systems are made,
the windings should be checked for insulation resistance and, if the
resistance is low, the windings should be cleaned andjor dried.
Main motors should be checked for proper direction of rotation
before coupling to the driven equipment, especially if the equip­
ment may be damaged by incorrect rotation. Auxiliary motors
(blower, oil pump, etc.) should be checked for proper rotation
before starting the main motor or generator.
Space heaters, inspection lights and electric outlets, as fur­
nished, should be wired to a source of power of the voltage and
frequency specified on the outline drawing. The space-heater
circuit should include a switch, either manual or automatic, to tum
on the heaters whenever the machine is shut down.
Thermal-sensitive switches (if furnished) are wired to a com­
mon point, as shown on the outline drawing. The terminals are
marked with a letter followed by a subscripted number to identify
the particular switch. Resistance temperature detectors, if fur­
nished, are wired to a special terminal board. Connections to this
terminal board are usually described on the outline drawing.
GROUNDING
Motor or generator and control wiring, overload protection and
grounding should be in accordance with the National Electric
Code and consistent with sound local practices. Failure to observe
these precautions may result in damage to the equipment, injury to
personnel, or both. The ground conductor size should be selected
to safely carry the maximum fault current available from the
source for the time required to interrupt the fault current. Refer to
the outline drawing for recommendation.
INITIAL STARTING
Prestart Inspection
The following are suggested as some of the items which are most
frequently overlooked and which should be checked before start­
ing a machine for the first time, or after an extended shutdown.
The voltage on the nameplate corresponds with the line
voltage.
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The journal packing has been removed (on machines shipped
assembled); bearing-pedestal insulation has been checked; the oil
scraper or rings are in place; the journal, bearing-pedestal and oil
lines have been properly cleaned; and joints and oil plugs are
sealed and tight.
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Oil level in all bearings is correct. All necessary oil and water
piping is complete and operative, and the check valve in the
bearing lift-pump pipe, where used, is installed and is functioning
properly. Pour a pint of oil into the bearing through the inspection
opening immediately before start, so the bearing will not start up
dry. Oil viscosity is correct for the application.
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It should be recognized that certain limitations in sleeve-bearing
speeds are necessitated by the hydrodynamic process in the bear­
ing. The oil film between the shaft journal and the bearing
necessary to prevent a "dry", i.e., metal-to-metal contact, bearing
operation can only be developed and maintained above a certain
minimum bearing rotational speed. This minimum speed is a
function of the bearing load, the oil viscosity and the bearing
configuration. Failure to develop the oil film will result in bearing
wipe.
The motor outline drawing usually specifies the permissible
minimum operational speed for the particular unit and the required
oil viscosity necessary for the operation. Below this minimum
speed no lubricating-oil film can be maintained with the specified
oil viscosity, and bearing wipe can be expected to occur. If it is
desirable to run below the minimum speed for any length of time,
oil with higher viscosity is required or the bearing should be
supplied with a bearing lift pump, which automatically lifts the
bearing journal and supplies oil between the journal and the
bearing at speeds where the hydrodynamic lubrication cannot
exist.
For the reasons listed above, motors and generators with sleeve­
type bearings should be brought up to speed as quickly as possible,
unless they are equipped with bearing lift pumps. It is also
recommended that motors which, for some reason, are to operate
at minimum speed for extended periods of time be brought up
above appropriate minimum bearing speed, e.g., to base speed, and
run for some time to assure a well-oiled bearing operation. If the
bearing oil is replaced by oil of higher viscosity than that recom­
mended on the outline drawing, at the maximum operational speed
excessive bearing temperatures may be realized, which may dam­
age the bearing.
The interior of the stator frame, the rotor, the air gap, and the
spaces between the poles are clean and free of loose objects (bolts,
nuts, and tools).
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TUTORIAL ON LARGE MOTOR INSTALLATION AND STARTUP
All moving parts have sufficient clearance from the nearest
stationary parts, especially between the pole faces and the stator.
Carefully turning the rotor with a crane to check for interference
is recommended.
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All electrical clearances are in good condition, particularly
where bare conductors of opposite polarity approach each other.
Bend all brush pigtails to maintain adequate clearance from ground­
ed portions of the machine and from pigtails or bus bars of opposite
polarity.
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oil circulating. If oil-pressure starting is used, the pump should be
turned off when the machine is running. During the first several
hours of continuous operation, the bearing temperature should be
checked frequently. Maximum safe operational temperature should
not exceed 80°C.
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All bolts and nuts are tight and locking devices are positively
secured. Foundation bolts, frame, and bearing hold-down bolts are
tight. All frame and bearing-pedestal (or bracket) dowels are
installed. Steel shipping dowels are replaced with insulated
dowels where necessary and dowels installed in all bearing pedes­
tals and stator frames.
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All protective devices (over speed devices, bearing tempera­
ture relays, etc.) are connected and function properly.
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All electrical connections are in accordance with the wiring
diagram. Motor rotation is correct.
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Controller and protective relays are wired correctly and func­
tion properly.
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The cooling and ventilating system provides the specified
quantity and quality of ventilation per the outline drawing. Cov­
ers, inspection doors, and access doors of force ventilated ma­
chines are subject to substantial airflow forces. Use caution when
removing and replacing covers or when opening and closing
access doors when machine is rotating or energized or when
ventilating fans are operating.
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When the machine has been carefully inspected according to the
instructions outlined above, make the initial start by following the
regular sequence of starting operations given under the instruction
for the particular type of machine.
NO-LOAD INSPECTION
Check the bearing lubrication. If the bearings require cooling
oil, or if flood lubrication is used, the pumps should be running and
Check for undesirable rubbing interference, and correct if
found.
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Check the vibration amplitude at all operating speeds. Cor­
rect by balancing or realignment, if necessary.
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Check the running endplay, and dowel the frame before
loading the machine.
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Operate the unit at no-load for a time sufficient to detect and
eliminate any excess heating.
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CONCLUSIONS
Careful handling, proper inspection of all components, and
diligent attention to every detail are required to ensure the success­
ful installation and startup of large machines. The outlined step­
by-step procedures should be followed and all manufacturer
instructions adhered to. Prepared checklists should be in place and
each item logged as it is completed. These guidelines are also
largely applicable to machines that have been sent out for repair or
reconditioning. When being reinstalled, items already in place
should be rechecked, looking for signs of deterioration or damage
that may have been incurred during removal.
The production of an entire facility is often dependent upon the
reliable operation of large motors. If shortcuts are taken that result
in less than attainable reliability and performance, the possible loss
of product through unscheduled outages or reduced capacity will
soon offset any short term savings. The need to be competitive
requires that the best effort be expended for every task involved.
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PROCEEDINGS OF THE TWENTY-SECOND TURBOMACHINERY SYMPOSIUM